# NAG Library Routine Document

## 1Purpose

To supply individual optional parameters to e04ncf/e04nca. More precisely, e04nef must be used to supply optional parameters to e04ncf and e04nea must be used to supply optional parameters to e04nca.
e04nea is a version of e04nef that has additional arguments in order to make it safe for use in multithreaded applications (see Section 5). The initialization routine e04wbf must have been called before calling e04nea.

## 2Specification

### 2.1Specification for e04nef

Fortran Interface
 Subroutine e04nef ( str)
 Character (*), Intent (In) :: str
#include nagmk26.h
 void e04nef_ ( const char *str, const Charlen length_str)

### 2.2Specification for e04nea

Fortran Interface
 Subroutine e04nea ( str,
 Integer, Intent (Inout) :: iwsav(610) Integer, Intent (Out) :: inform Real (Kind=nag_wp), Intent (Inout) :: rwsav(475) Logical, Intent (Inout) :: lwsav(120) Character (*), Intent (In) :: str
#include nagmk26.h
 void e04nea_ ( const char *str, logical lwsav[], Integer iwsav[], double rwsav[], Integer *inform, const Charlen length_str)

## 3Description

e04nef/e04nea may be used to supply values for optional parameters to e04ncf/e04nca. It is only necessary to call e04nef/e04nea for those arguments whose values are to be different from their default values. One call to e04nef/e04nea sets one argument value.
Each optional parameter is defined by a single character string, of up to $72$ characters, consisting of one or more items. The items associated with a given option must be separated by spaces, or equals signs $\left[=\right]$. Alphabetic characters may be upper or lower case. The string
`Print Level = 1`
is an example of a string used to set an optional parameter. For each option the string contains one or more of the following items:
 – a mandatory keyword; – a phrase that qualifies the keyword; – a number that specifies an integer or real value. Such numbers may be up to $40$ contiguous characters in Fortran's I, F, E or D formats, terminated by a space if this is not the last item on the line.
Blank strings and comments are ignored. A comment begins with an asterisk (*) and all subsequent characters in the string are regarded as part of the comment.
For e04nef, each user-specified option is normally printed as it is defined, on the current advisory message unit (see x04abf), but this printing may be suppressed using the keyword Nolist. Thus the statement
```Call e04nef ('Nolist')
```
suppresses printing of this and subsequent options. Printing will automatically be turned on again after a call to e04ncf and may be turned on again at any time using the keyword List.
For e04nea printing is turned off by default, but may be turned on at any time using the keyword List.
Optional parameter settings are preserved following a call to e04ncf/e04nca and so the keyword Defaults is provided to allow you to reset all the optional parameters to their default values before a subsequent call to e04ncf/e04nca.
A complete list of optional parameters, their abbreviations, synonyms and default values is given in Section 12 in e04ncf/e04nca.

None.

## 5Arguments

1:     $\mathbf{str}$ – Character(*)Input
On entry: a single valid option string (as described in Section 3 and in Section 12 in e04ncf/e04nca).
Note: the following are additional arguments for specific use with e04nea. Users of e04nef therefore need not read the remainder of this description.
2:     $\mathbf{lwsav}\left(120\right)$ – Logical arrayCommunication Array
3:     $\mathbf{iwsav}\left(610\right)$ – Integer arrayCommunication Array
4:     $\mathbf{rwsav}\left(475\right)$ – Real (Kind=nag_wp) arrayCommunication Array
The arrays lwsav, iwsav and rwsav must not be altered between calls to any of the routines e04nea, e04nca, e04nda or e04wbf.
5:     $\mathbf{inform}$ – IntegerOutput
On exit: contains zero if a valid option string has been supplied and a $\text{value}>0$ otherwise (see Section 6).

## 6Error Indicators and Warnings

${\mathbf{inform}}=5$
The supplied option is invalid. Check that the keywords are neither ambiguous nor misspelt.

Not applicable.

## 8Parallelism and Performance

e04nef/e04nea is not threaded in any implementation.